1. Field of the Invention
The present invention relates to a method of regenerating an ink image recording medium, which is applied for an ink image recording system for recording ink images onto a transfer sheet by the thermal energy to which electric signals are converted.
2. Description of the Related Art
There is an ink image recording system of the current feed thermal transfer type in which an ink image is recorded by using an ink image recording medium having a multilayered structure consisting of an anisotropic conductive layer, a heating resistive layer for generating heat by an electric signal corresponding to an image signal, a conductive layer, and a heat-fusible ink surface-layer. After the ink image is transferred to the transfer sheet, the ink of the heat-fusible ink surface-layer of the ink image recording medium is partially lost because of the image transfer. In the image recording system, however, the ink image recording medium with the ink-lost ink layer is regenerated by supplying new ink to the ink-lost ink layer, and the regenerated ink image recording medium is used again.
FIG. 4 is a schematic view showing the ink image recording system. As shown in FIG. 4, an ink image recording medium 10 is transferred in the direction of an arrow B by transfer rolls 41. In a printer section 20, to print an ink image, the heat-fusing ink of the recording medium 10 is transferred onto an image-transferred sheet 23 lying on a back pressure roll 22, according to an electric signal from a recording head 21. The signal current flows to a ground point, by way of a return contact roll 26. Then, the ink recording medium 10 reaches an ink supply unit 30 where the recording medium is supplied with powder ink. Thereafter, the resultant recording medium is transferred to an ink layer smoothing unit 40. In the unit 40, the surface of the heat-fusible ink surface-layer is smoothed to complete the regeneration of the image recording medium. The regenerated recording medium is then used in the next image recording operation.
In the ink image recording system as stated above, when the ink image recording medium is regenerated, the heat-fusible ink powder sticks not only to the transferred portions, that is, the portions of the heat-fusible ink surface-layer where the ink has been transferred, but also to the non-transferred portions, that is, the portions where the ink is left. Accordingly, the ink layer of the regenerated ink image recording medium loses much of its thick uniformity. Because of the nonuniformity, the regenerated recording medium cannot be used repeatedly for a long time.
To solve the problem, there is a proposal in which the heat-fusible ink surface-layer is charged to the same polarity as that of the voltage of the charged ink particles, thereby to allow the powder ink to stick to only the transferred portions of the heat-fusible ink surface-layer. However, the proposal is still unsatisfactory in that a relatively high voltage is required, and that it is difficult to form a thin and uniform ink layer.